The draft IEEE Standard for Local and Metropolitan Area Networks: Virtual Bridged Local Area Networks (IEEE P802.1Q-2006/D0.1) specifies that a VLAN aware Bridge includes a Media Access Control (MAC) Relay Entity that interconnects the Bridge's Ports, at least two Ports, and higher layer entities, including at least a Spanning Tree Protocol Entity. The MAC Relay Entity handles the media access method-independent functions of relaying frames among Bridge Ports, filtering frames, and learning filtering information. The MAC Relay Entity uses the Enhanced Internal Sublayer Service (EISS) provided by each Bridge Port.
Each Bridge Port can also function as an end station providing one or more instances of the MAC Service. Each instance of the MAC Service is provided to a distinct Logical Link Control (LLC) Entity that supports protocol identification, multiplexing, and demultiplexing for PDU transmission and reception by one or more higher layer entities.
Bridges identify Layer 2 Control Protocols (L2CPs) by the “type” field following the MAC addresses in the protocol frames. The destination address of a L2CP frame determines the span of connectivity of the frame and thus to which ports it is delivered. Thus, the relay function within a bridge forwards or filters the frame according to the destination address, regardless of the type. A given protocol only operates on frames containing a “type” field corresponding to that given protocol; however the protocol may also use other criteria to determine what operation, if any, is to be performed. These criteria may include the destination address, VLAN ID, and/or fields within the MAC Service Data Unit (SDU). How these criteria are used in determining how to process a frame is protocol dependent. The determination by the protocol entities of whether or not to process a frame is independent of whether the frame is forwarded or filtered by the relay.
The connectivity of the Higher Layer Entities to the other bridge entities as currently specified in Section 8.5 of IEEE Std 802.1Q, cannot meet the demands required by complex types of ports such as the ports on a Provider Backbone Edge Bridge (BEB). The BEB ports are described in the draft IEEE Standard for Local and Metropolitan Area Networks—Virtual Bridged Local Area Networks—Amendment 06: Provider Backbone Bridges (IEEE P802.1ah/D3.3, December 2006). Frames initiated by or destined to Higher Layer Entities that are attached on a Provider Instance Port (PIP) or a Customer Backbone Port (CBP) would not reach their intended peer entities if they are not properly tagged. In addition, BEBs do not have the capability of tunneling, discarding, or peering the L2CPs initiated by the attached customer networks. Current specifications also fail to provide a mechanism that would allow Higher Layer Entities to communicate over an External Network-to-Network Interface (E-NNI). Enhancements are needed to the Bridge Port Connectivity functionality described in IEEE Standard 802.1Q in order to address these issues.
What is needed in the art is a system, method, and Bridge that helps alleviate the problems associated with the issues outlined above. The present invention provides such a system, method, and Bridge.